Consciousness describes three things. We know these not by first defining consciousness but by taking something obviously conscious (me) and isolating the elements essentially conscious within it.
1.) The reflectively conscious. Such a being is aware not only of an exterior world and of its own body, but is aware of consciousness as well and so is capable of comparing the two. Such a being therefore knows truth and falsity, and is capable of building up a vast corpus of interconnected truth – science, wisdom, etc..
2.) The simply conscious. Such a being is aware of the exterior world and its own body, but not of its own awareness. It acts and behaves without ever comparing its consciousness to the world. Lacking this comparison, it never develops sciences, though it is certainly capable of signaling and of communication, since signs can be just as objective as the trees, sun, or predators in his world. There is also no impediment to such a being developing tools, since one does not need any theory of the world in order to manipulate it. Such a consciousness requires the familiar apparatus of a nervous system, brain, etc.
3.) The immanently conscious. At this level awareness of both awareness and an exterior world falls away, and the being is conscious only of its own interior world. Ruyer compared this level of consciousness to the workman absorbed in a task, though the task is, from our perspective, not an action on the world but on its own body; but it is just as true to say that the body of the immanently conscious being is a universe. The being preserves itself and nourishes itself with food that, from its own perspective, arises spontaneously within it in the same way that we see that food arises in the universe. In doing this being disposes the parts of itself with an eye to accomplishing certain tasks and so is by definition conscious. Such a consciousness does not demand a nervous system, brain, etc. While I myself am confident that we can divide the living from the non-living, it is not appropriate to limiting the immanently conscious, which penetrates to the lowest level of material organization and to anything that counts as a substance or organized part of substance (the stability of the atom)
We are familiar with this level of consciousness because we can make sense of speaking of “the brain thinking”, i.e. co-ordiating its behaviors and actions finalistically in order to accomplish some task. The activity of the brain, however, is thought without a nervous system since the nervous system knows without requiring a second nervous system to accomplish this.
Machines are on this account extensions of consciousness. There is no reason to assume that consciousness can exist without these extensions since we have extensive experience with machines being sine qua nons of existence (hospital life-support machines, scuba equipment, space suits, etc.) Nevertheless, it is wrong to identify consciousness with its extension into the world. Machines are tools and therefore essentially extensions of action, whether it extends an arm like a crane, a stick to fish for termites, or even the hand. The lever of a carjack, a dog door, and the elbow are all extensions of some modality of consciousness.